1. Field of the Invention
The present invention relates to the field of fluid control systems, and more particularly to the field of automatic sprinkler systems.
2. Prior Art
The present invention is primarily directed toward use as an automatic sprinkler system and component parts thereof, and thus the following discussion of the prior art shall be so limited. In particular, the present invention comprises primarily a unique configuration for a pilot controlled valve and a unique system, including control electronics, for utilizing the valve to achieve a highly accurate, very reliable and low cost automatic sprinkler control system. Thus the prior art relating to pilot actuated valve configurations and control systems, and more particularly battery operated control systems is most relevant to the present invention.
Most prior art sprinkler valves and systems for automatic operation which are presently is use are intended for driving by a common 110 V. 60 Hz. power, typically through a mechanical time clock and step down transformer. Such systems have good reliability, and at least the component parts thereof may be manufactured at a reasonable cost. However, typically installation is very expensive for new homes, and may be prohibitive in established homes because of the necessity of running some form of electrical line under sidewalks, lawns, trees and the like. Accordingly, in recent years various designs for battery operated sprinkler control systems have been proposed which effectively eliminate these otherwise severe installation problems.
One such prior art battery operated system is that of U.S. Pat. No. 3,821,967. This type of system uses a latching actuator to control a pilot valve to actuate a main valve member cooperating with a valve seat, typically already in the sprinkler line, such as the valve seat associated with the manual valve portion of an anti-siphon valve. The latching actuator and pilot valve assembly is mounted to the side of the main actuator assembly so as to control the venting of water from the top to the bottom of the pressure responsive member (a diaphragm in the specific patent referred to). The entire system is turned on by a pulse derived from a crystal oscillator and count-down chain, with the system being turned off by a unijunction time delay circuit initiated by the turn on signal. Additional units in a group of units may only have the unijunction time delay circuit therein, with each such unit having a provision for receiving an initiating signal to trigger the opening of the valve, and to provide an initiating signal to the next valve upon its closing. This, together with the providing of an initiating signal with the closing of the valve having the crystal oscillator therein, allows for the sequential operation of an unlimited number of valves, based upon a single crystal oscillator input. Thus, each valve in such a chain comprises not only the valve but in addition at least a time delay circuit and power supply to operate the latching actuator, with the first unit in the chain also having the master time clock comprised of a crystal oscillator and count-down chain.
The foregoing system has a number of advantages. In particular, installation is very easy, the crystal oscillator is very accurate, and battery life is relatively long. In addition only one master oscillator is required for any group of valves, and yet sequential operation may readily be achieved by a simple interconnection of adjacent valves to provide sequential operation for maximum use of normally limited water supply delivery rates. Such a system, however, has certain disadvantages also. In particular the maximum watering time achievable by unijunction oscillators using components of reasonable cost is limited, and the water duration is not very accurate unless calibrated. In addition the valve mechanical configuration and the design and arrangement of the latching actuator and pilot mechanism are not of the simplest design, resulting in a larger number of parts than necessary, and having sensitivities to adjustments requiring assembly and test time. As a result, the design of the foregoing patent, while solving a great number of problems of the prior art, is now a low cost design, is limited in watering duration achievable and the accuracy of the watering duration selected.
Another type of battery operated sprinkler system is that disclosed in U.S. Pat. No. 3,547,154. That system uses a battery to operate a motor driven timer which periodically rotates a permanent magnet on a timer disc into proximity with a magnetically actuated read switch, which turns on a solenoid valve and a time delay network, which in turn turns off the solenoid valve after the desired time. This system is rather mechanically and electronically complex and requires relatively large batteries, such as wet storage cells. It further has no provision for operating a plurality of valves in sequence from a single timer. While various specific valve configurations are known for use in such systems (see U.S. Pat. Nos. 3,460,798; 3,785,612; 3,858,841; 3,412,970; 3,410,301; and 3,363,433) such valves are mechanically complex and consume too much power for battery operation. Thus there is a need for valves for fluid control system which are mechanically simple and inexpensive to manufacture, and which consume a minimum of power so as to be suitable for battery operation.